CASTING UNIT AND CASTING METHOD
The casting unit solves problems of a conventional casting unit, in which a non-consumable sprue is connected to a lost foam gate attached to a core, such as troublesome assembly and post-treatment after casting. In the casting unit, a plurality of cores having molten metal inlets, which open into the surfaces of the cores and through which a molten metal is caused to flow into cavities formed in the cores, and a lost foam pattern, which forms a sprue between each of the molten metal inlets and a sprue cup, in which a molten metal is poured, and which has a peripheral surface coated with a refractory mold coating agent, are embedded in dry sand except for the sprue cup, and the cores, which are adjacent to each other, are connected to each other so that the plurality of cores are integrated.
The present invention relates to a casting unit and a casting method.
BACKGROUND OF TECHNOLOGYA conventional casting method in which a lost foam pattern composed of resin, e.g., styrene foam, is used is known.
In the above described conventional method, a casting unit shown in
A tubular member 110 having a plurality of through-holes 110a, 110a, . . . , whose diameter is smaller than a grain diameter of the dry sand 106, is inserted in the dry sand 106 so as to collect and discharge a decomposition gas, which is generated by contact between the lost foam pattern and the molten metal.
In the conventional casting method using the casting unit shown in
Note that, the decomposition gas from the resin, e.g., styrene foam, is introduced into the tubular member 110, via gaps between grains of the dry sand 106, and discharged to the outside.
In the conventional casting method using the casting unit shown in
In case that the product sections 102 are large, a part of the lost foam pattern will be left or soot will be generated. If the left part of the lost foam pattern or the soot is included in the cast products. The cast products including the left part of the lost foam pattern or the soot must be treated as bad products.
Besides the above described conventional casting method using the lost foam pattern, Patent Document 1 discloses another conventional casting method performed in a casting unit shown in
In the casting unit shown in
Further, a film 214 for depressurization sealing covers a surface of the dry sand 208.
PRIOR ART DOCUMENT Patent DocumentPatent Document 1: Japanese Laid-open Patent Publication No. P6-226422
SUMMARY OF THE INVENTION Problems to be Solved by the InventionIn case of using the casting unit shown in
Decomposition gasses, which are generated by thermally decomposing the resins of the lost foam gate 206 and the core 202, are discharged from the depressurizing wire mesh pipe 212 via gaps between grains of the dry sand 208.
In the casting unit shown in
However, in the casting unit shown in
In case of using a plurality of cores, a non-consumable branch pipe or pipes are required, so the assembly and the post-treatment must be more troublesome.
An object of the present invention is to provide a casting unit and a casting method, which are capable of: solving the problems of the conventional casting units, in which the non-consumable sprue is connected to the lost foam gates of the cores, such as troublesome assembly and post-treatment after casting; preventing vestiges of resin grains from being transferred onto surfaces of cast products; preventing a part of lost foam pattern from being left in the products; preventing generation of soot; and easily performing the assembly and the post-treatment after casting.
Means for Solving the ProblemsThe inventors of the present invention have studied to solve the above described problems of the conventional casting units, and they found that even if the entire sprue connecting a plurality of cores, in which cavities are formed, to a sprue inlet was formed as a lost foam pattern, an amount of resin for forming the lost foam pattern could be less than that of the resin for forming the lost form pattern shown in
Further, the inventors found that the plurality of cores could be treated as one body by connecting and integrating the adjacent cores, so that they reached the present invention.
To solve the above described problems, the inventors provide a casting unit comprising: a plurality of cores having molten metal inlets, which open into the surfaces of the cores and through which a molten metal is caused to flow into cavities formed in the cores; and a lost foam pattern forming a sprue between each of the molten metal inlets and a sprue inlet, in which a molten metal is poured, the lost foam pattern having a peripheral surface coated with a refractory mold coating agent, wherein the cores and the lost foam pattern are embedded in dry sand except for the sprue inlet, and wherein the cores, which are adjacent to each other, are connected to each other so that the plurality of cores are integrated.
Further, the inventors provide a casting method performed in the casting die of the present invention, comprising the steps of: plasticizing the dry sand, by applying vibration, after pouring the molten metal into the sprue inlet; and pulling a cast body, in which runners, which are formed by filling the sprue formed by the lost foam pattern with the molten metal, and products, which are formed by filling the cavities of the cores with the molten metal, are integrated, out of the dry sand.
As to the casting unit and the casting method provided by the inventors, preferable aspects will be explained.
By connecting the cores, which are adjacent to each other, to each other by an adhesive or concavo-convex engagement, the plurality of cores can be easily connected and integrated.
By constituting each of the cores by a pair of core molds, the cores in which the cavities are respectively formed can be easily produced. Preferably, the cores are constituted by shell molds, self-hardening molds or combination of the both.
In case that the cores are constituted by the shell molds, the plurality of the cores can be highly easily connected by bringing softened layers of the shell molds, in which resin included in the shell sand is softened, into tight contact with each other and hardening the softened layers.
By coating inner wall faces of the cavities formed in the cores with a refractory mold coating agent, the casting can be performed with a high temperature molten metal.
Further, the casting unit can be downsized by: inserting the cores, the sprue, the sprue inlet and the dry sand into a metal flask; and inserting a tubular member having a plurality of through-holes, whose diameter is smaller than a grain diameter of the dry sand, into the dry sand so as to collect and discharge a decomposition gas, which is generated by contact between the cores, the lost foam pattern and the molten metal.
Effects of the InventionIn the casting unit invented by the inventors, even if the sprue, which connects each of the cores in which the cavities are formed to the sprue inlet, is formed by the lost foam pattern, the resin of the lost foam pattern can be fully thermally decomposed by the molten metal poured into the sprue inlet, and the thermally-decomposed gas can be discharged to the outside via the cores and gaps between grains of the dry sand. Therefore, leaving a part of the lost foam pattern and generating soot can be prevented, so that invasion of the lost foam pattern or soot into cast products can be prevented.
The plurality of cores can be integrated by connecting the cores, which are adjacent to each other, to each other, so that the integrated cores can be treated as one body and the integrated cores can be easily handled when the casting unit is assembled.
After casting, the cast products, which are formed by filling the cavities with the molten metal, and the runners, which are formed by filling the sprue with the molten metal, are integrated as one cast body. Therefore, the cast body can be easily pulled out from the dry sand.
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An embodiment of the casting unit relating to the present invention is shown in
By coating inner wall faces of the cavities 14 with a refractory mold coating agent, a high temperature molten metal, e.g., molten stainless steel, can be used for casting.
Note that, the pair of core molds 12a and 12b may be constituted by shell molds, self-hardening molds or combination of the both.
Further, the cores 12 and 12 shown in
A sprue is formed, by a lost foam pattern 20, between the ingates 16, which are respectively provided to the cores 12 and 12, and a sprue cup 18, i.e., sprue inlet, composed of ceramic. The lost foam pattern 20 is composed of resin, e.g., styrene foam. An inverted triangle part 20a of the lost foam pattern 20, which contacts the ingates 16 and 16 of the cores 12 and 12, is thicker than other parts of the lost foam pattern 20 and forms a feeder head. In case that the inverted triangle part 20a is located on the parting lines of the cores 12 and that the cores and 12 are integrated, the inverted triangle part 20a contacting the ingates 16 and 16 of the cores 12 and 12 may be a cast mold integrated with the cores 12 and 12 instead of the lost foam pattern.
Note that, the sprue cup 18 may be a shell mold or a self-hardening mold.
Further, lost foam patterns 22, which form discharging feeder heads, are respectively connected to communication holes, which are respectively opened in upper faces of the cores 12 and 12 and communicated to the cavities 14. The communication holes are formed on the parting lines of the cores 12 shown in
Outer faces of the lost foam patterns 20 and 22 are coated with a refractory mold coating agent, which is not molten or thermally decomposed by the molten metal poured into the sprue cup 18. Therefore, when the lost foam patterns 20 and 22 are thermally decomposed and disappeared by the molten metal poured into the sprue cup 18, the refractory mold coating agent forms outer faces of the sprue and the discharging feeder heads.
Note that, the inverted triangle part 20a of the lost foam pattern 20 is connected to parts of the cores 12 and 12 including the ingates 16 and 16 by an adhesive.
In the casting unit shown in
A tubular member 26, which has through-holes 26a, 26a, . . . , whose diameter is smaller than a grain diameter of the dry sand 24, is inserted in the dry sand 24. The tubular member is used to collect and discharge decomposition gasses, which are generated by contact between the cores 12 and 12, the lost foam patterns 20 and 22 and the molten metal.
Embedding the cores 12 and 12 and the lost foam patterns 20 and 22 in the dry sand 24 is performed by filling the flask 10, in which the cores 12 and 12 and the lost foam patterns 20 and 22 have been inserted, with a prescribed amount of the dry sand 24 and then applying vibration to the flask 10, or by filling the flask 10 with the dry sand with applying vibration thereto, so that gaps between the cores 12 and 12 and the lost foam patterns 20 and 22 can be filled with the dry sand 24.
By pouring the molten metal into the sprue cup 18 of the casting unit as shown in
The molten metal poured into the sprue 32 is introduced into the cavities 14 of the cores 12, via the ingates 16 of the cores 12 and 12 so as to fill the cavities. Further, the molten metal in the cavities 14 contacts the lost foam patterns 22 connected to the communication holes of the cavities 14, so that the lost foam patterns 22 are disappeared and the discharging feeder heads 34 are formed.
When the molten metal fills the cavities, resins of the lost foam patterns 20 and 22 and the cores 12 and 12 are thermally decomposed by the heat of the molten metal, and decomposition gasses are generated. The decomposition gasses are collected in the tubular member 26, via gaps between grains of the dry sand 24 and the through-holes 26a, 26a, . . . , and discharged to the outside from an outlet of the tubular member 26.
Note that, by providing an ignition unit, e.g., sparking plug, to the outlet of the tubular member 26, the decomposition gasses discharged from the tubular member 26 can be burned.
When the cavities 14 of the cores 12 and 12 are filled with the molten metal, pouring the molten metal into the sprue cup 18 is stopped, and then the molten metal in the cavities 14 is cooled.
While cooling the molten metal in the cavities 14, gaps will be formed in the cavities 14 by shrinkage of the molten metal being cooled. But, the gaps can be filled with the molten metal stored in the feeder head 32a or the discharging feeder heads 34.
When cooling the molten metal in the cavities 14 is completed, a cast body, in which cast products P formed in the cavities 14 of the cores 12 and 12 and a cast runner 36 formed in the sprue 32 are integrated as shown in
The cast body can be pulled out from the dry sand 24 after the dry sand 24 is plasticized by applying vibration.
In the cast body 30 shown in
By patting the cores 12 and 12 of the cast body 30, the cores 12 and 12 can be separated from the cast runner 36, and the cores 12 and 12 are simultaneously broken, so that the cast products P and P can be taken out.
Cast discharging feeder head parts 40a and 40a, which are formed in the discharging feeder heads 34, are projected from outer faces of the cast products P and P taken out from the cores 12 and 12. The cast discharging feeder head parts 40a and 40a can be easily cut and removed.
As described above, the cores 12 and 12 are integrated by the adhesive, and the cores 12 and 12 can be handled as one body, so that the casting unit shown in
The cast products P and P have smooth surfaces, and invasion of parts of the lost foam patterns 20 and 22 or soot into the cast products can be prevented.
When the cores 12 and 12 are separated from the cast runner 36, even if the cores 12 and 12 are not broken, components of the cores 12 and 12 contact the molten metal, organic matters, e.g., adhesive, are thermally decomposed and adhesive strength is lowered, so that the cores 12 and 12 can be easily broken and the cast products P and P can be easily taken out.
In
The inverted triangle part 20a, which is formed at a core 12 side end of the lost foam pattern 20 forming the sprue, is formed for forming the feeder head and connected to the ingates 16 of the center cores 12 and 12 of the arranged cores 12, 12, . . . .
Further, lost foam patterns 20b and 20b are extended, from the part 20a provided to the center cores 12 and 12, toward the adjacent cores 12, 12, . . . . The inverted triangle parts 20a are formed at prescribed positions of the lost foam patterns 20b and 20b and respectively connected to the ingates 16 of the adjacent cores 12, 12, . . . .
By using the cores 12, 12, . . . and the lost foam patterns 20, 20a and 20b, the cast product 30, in which the six cores 12, 12, . . . , in which the cast products P are formed, are connected to the lower end of the cast runner 36, can be obtained.
In
In case of using the cores 12, 12, . . . shown in
When the concave parts 50 of the core 12 and the convex parts 52 of the adjacent core 12 are concavo-convex-engaged, an adhesive may be applied to the engaged parts.
Further, as to the adjacent cores 12, 12, . . . shown in
In case of using the core 12 constituted by a pair of shell molds, the cores 12, which are adjacent to each other, can be connected to each other by tightly adhering their softened layers, in each of which a resin included in shell sand is softened, to each other.
A casting mold which is formed by a shell molding method with using the shell sand is generally called “shell mold”, and the shell sand is dry sand which is mixed with powders of the resin, e.g., phenol resin, hexamine. The shell sand is granulated at room temperature and softened by increasing temperature to the melting point of the resin. The softened shell sand is hardened by further increasing the temperature.
The core constituted by the pair of shell molds is produced by the steps of: applying vibration to the shell sand; pressing a pair of molds, which are heated, into the shell sand, which is being vibrated, from above; leaving the pair of molds in the shell sand for a prescribed period of time; lifting the shell molds, in each of which a hardened layer being hardened on a molding face and a softened layer, which covers the hardened layer and in which the resin included in the shell sand is softened, are formed, from the shell sand; and tightly adhering the softened layers to each other.
Details of the above described method of producing the shell molds will be explained with reference to the drawings.
As shown in
By applying vibration to the shell sand 85 by the vibrator 88, frictional resistance between grains of the shell sand 85 can be reduced and the shell sand can be plasticized, so that a pair of molds 82 and 84 can be easily pressed into the shell sand 85 from above.
The molds 82 and 84 to be pressed into the shell sand 85 are located above the shell sand container 21, and their molding faces 51 and 54 are faced downward. Rear faces (opposite sides of the molding faces, i.e., upper faces) of the molds 82 and 84 are formed in concave portions 19, which are concaved toward the molding faces.
Chambers 86, which are isolated from the outside, are respectively formed in upper parts (rear side parts) of the molds 82 and 84 including the concave portions 19. Heating means, e.g., heaters 80, are respectively provided in the chambers 86. The heaters 80 are, for example, electric heaters and capable of heating air in the chambers 86.
Each of the chambers 86 is constituted by a frame 27, which is vertically extended from an upper part of the mold 82 or 84 and encloses the chamber 86, and a top plate 53, which covers an upper face of the frame 27. As to each of the chambers 86, the mold 82 or 84 constitutes a bottom part, the frame 27 constitutes side walls, and the top plate 53 constitutes a top part, namely the frame 27 and the top plate 53 are included in each of chamber constituting sections.
The molds 82 and 84 are respectively fixed to flanges 13, each of which is inwardly extended from the frame 27, by bolts, etc. The molds 82 and 84 may be composed of a material with high heat conductivity, e.g., aluminum. Aluminum is lighter than other metals, so the concave portions 19 composed of aluminum are capable of reducing their weights and can be easily handled.
Ejector pins 78, which eject completed shell molds A and B (see
Upper end parts of the ejector pins 78 pass through each of the top plates 53. The upper end parts of the ejector pins 78, which pass through the top plate 53, are fixed to each of the press plates 56. Lower end parts of the ejector pins 78 can be projected from and retracted into through-holes of each of the flanges 13. Lower end faces of the ejector pins 78 are usually level with bottom faces of each of the flanges 13.
Each of the press plates 56 is located above each of the top plates 53 and always biased upward, with respect to each of the top plates 53, by biasing means 59, e.g., springs.
Press cylinder units 58, which actuate the ejector pins 78, are respectively provided above the press plates 56. Each of the press cylinder units 58 is located above each of the press plates 56, fixed to each of cylinder frames 60, and each of rods 58a is fixed to each of the press plates 56.
By actuating the press cylinder units 58, the rods 58a move the press plates 56 downward against biasing force of the biasing means 59. Then, the ejector pins 78, which are fixed to the press plates 56, are moved downward and projected from the through-holes. The ejector pins 78, which are projected from the through-holes, eject the shell molds A and B (see
In the above described embodiment, inner spaces of the chambers 86 are heated by the heaters 80, so leakage of the heated air from the chambers 86, via the through-holes of the top plate 53 and the flanges 13 through which the ejector pins 78 pass, may be ignored.
Note that, in case of spraying overheated steam or heated air into the chambers 86, inner pressures of the chambers 86 are increased, so the through-holes of the top plate 53 and the flanges 13, through which the ejector pins 78 pass, must be tightly sealed so as to prevent the overheated steam or heated air from leakage. Preferably, in this case, the ejector pins 78 are enclosed by constituting members of the frames 27 or the molds 82 and 84 so as not to expose the ejector pins 78 in the chambers 86.
Each of the chamber constituting sections, which includes the molds 82 or 84, is attached to a robot arm 70 of each of articulated robots and capable of rotating in the vertical plane, moving in the horizontal plane and moving upward and downward.
Turning means 71, e.g., motor, is provided to each of the robot arms 70, and a rotary shaft of the turning means 71 is connected to each of the chamber constituting sections. By actuating each of the turning means 71, bottom faces of the shell molds formed on the molding faces of the molds 82 and 84 can be faced each other.
In each of the robot arms 70, turning means 72, whose rotary shaft is arranged perpendicular to the rotary shaft of the turning means 71, is provided on the upper side of turning means 71. Further, turning means 74, whose rotary shaft is arranged parallel to the rotary shaft of the turning means 71, is provided on the upper side of turning means 72.
By actuating the turning means 72, the molds 82 and 84 can be moved in the direction perpendicular to a paper surface of the drawing of
By actuating the turning means 71 and 74, the molds 82 and 84 can be moved in the vertical direction and horizontal direction.
Upper ends of the robot arms 70 are not shown, but tuning means (not shown), whose rotary shafts are arranged in a prescribed direction, are attached to the upper ends, so that the molds 82 and 84 can be moved upward and downward by actuating the turning means of the robot arms 70.
For example, motors or cylinder units may be used as the turning means 71, 72 and 74.
A manner of connecting the shell molds will be explained with reference to
Firstly, in
The vibrator 88 is started to apply vibration to the shell sand 85 in the shell sand container 21 before the molds 82 and 84 are downwardly moved into the shell sand container 21.
As shown in
The heaters 80 maintains the temperatures of the chambers 86 at a prescribed temperature with measuring the current temperatures of the molds 82 and 84 by temperature sensors (not shown).
In
As shown in
In
In
In the state shown in
In
In
Finally, as shown in
The softened layers including the softened resin are tightly contacted each other in the process of producing the shell molds, so that the plurality of shell molds can be easily produced, by the above described connecting manner, in comparison with the manner in which the adjacent cores are connected by an adhesive or concavo-convex engagement.
Claims
1. A casting unit, comprising: a plurality of cores having molten metal inlets, which open into the surfaces of the cores and through which a molten metal is caused to flow into cavities formed in the cores; and a lost foam pattern forming a sprue between each of the molten metal inlets and a sprue inlet, in which a molten metal is poured, the lost foam pattern having a peripheral surface coated with a refractory mold coating agent, wherein the cores and the lost foam pattern are embedded in dry sand except for the sprue inlet,
- the casting unit is characterized in that the cores, which are adjacent to each other, are connected to each other so that the plurality of cores are integrated.
2. The casting unit according to claim 1, wherein the cores, which are adjacent to each other, are connected to each other by an adhesive or concavo-convex engagement.
3. The casting unit according to claim 1, wherein each of the cores is constituted by a pair of core molds.
4. The casting unit according to claim 1, wherein the cores are constituted by shell molds, self-hardening molds or combination of the both.
5. The casting unit according to claim 4, wherein the cores are constituted by the shell molds, and
- wherein the cores, which are adjacent to each other, are connected to each other by bringing softened layers of the shell molds, in which resin included in the shell sand is softened, into tight contact with each other and hardening the softened layers.
6. The casting unit according to claim 1, wherein inner wall faces of the cavities formed in the cores are coated with a refractory mold coating agent.
7. The casting unit according to claim 1, wherein the cores, the sprue, the sprue inlet and the dry sand are inserted in a metal flask, and a tubular member having a plurality of through-holes, whose diameter is smaller than a grain diameter of the dry sand, is inserted in the dry sand so as to collect and discharge a decomposition gas, which is generated by contact between the cores, the lost foam pattern and the molten metal.
8. A casting method being performed in the casting die of any one of claims 1-7, said method comprising the steps of: plasticizing the dry sand, by applying vibration, after pouring the molten metal into the sprue inlet; and
- pulling a cast body, in which runners, which are formed by filling the sprue formed by the lost foam pattern with the molten metal, and products, which are formed by filling the cavities of the cores with the molten metal, are integrated, out from the dry sand.
Type: Application
Filed: Jul 29, 2010
Publication Date: Apr 26, 2012
Inventor: Muneyoshi Terashima (Chikuma)
Application Number: 13/383,313
International Classification: B22C 9/10 (20060101); B22D 23/00 (20060101);